This application claims the priority of Application No. 2000-29917, filed Feb. 8, 2000 in Japan, the subject matter of which is incorporated herein by reference.
The present invention relates to a bending machine for bending leads of an electric part, such as molded IC package. More particularly, the present invention relates to a bending die used for Z-bending an end portion of leads of a molded IC package, molded LSI package, etc.
The mainstream of LSI mounting methods has been shifting from the conventional method employing DIPs (Dual In-line Packages) to the so-called surface mounting method in which a leaded electric part or device package is electrically connected to a conductor provided on the surface of a printed wiring board without using through-holes for insertion of lead wires. This shift is made to cope with an increase in the number of gates or the like as a result of the improvements of LSI chips, i.e., the achievement of high integration density, the increase in the number of functions thereof, and the achievement of high speed operation. Examples of known surface-mounted packages include resin-sealed SOJ (Small Outline xe2x80x9cJxe2x80x9d) leaded packages and PLCCs (Plastic Leaded Chip Carriers). Leads that are used in these packages are bended in a J or L shape and therefore capable of being mounted directly on a printed wiring board (PWB).
In general, press working effects bending of lead wires of ICs. Since lead wires are extremely thin, they are weak or fragile and it is therefore necessary to use extreme care in bending them.
A conventional bending machine includes a bending die and a punch. The bending die is provided with an outer surface, which is flattened and coated with a hard material. A lead of an IC or LSI package is bended on and along the surface. The lead is plated with solder. The coating is made on the surface of the bending die so as to reduce friction between the lead and the surface, and therefore the amount of small pieces of solder peeled off the lead is reduced.
In operation, when the IC package is fed to the bending die, the root portion of the lead is placed on an upper surface of the bending die. Next, the punch goes down so that the lead is pressed from the root portion, thereby bending it into a substantially Z-like shape.
As described above, the lead is plated with solder or tin in order to improve the electric conductivity required when it is mounted on a printed wiring board (PWB) and to enhance the adhesion of solder used to connect the lead to the PWB.
According to the above described conventional bending machine, even if the hard coating is made on the surface of the bending die, the ends of leads are scratched due to the frictional contact with the surface while the bending process is carried out. If the plating on the lead is peeled off, the small pieces of plating would be stuck onto the bending die, and then the plating pieces might be stuck back to the leads. If a large amount of plating is peeled off, a short circuit might be made between the leads.
Accordingly, an object of the present invention is to provide a bending die in which friction contact with a lead is remarkably reduced.
Another object of the present invention is to provide a bending machine in which friction contact between a bending die and a lead is remarkably reduced.
Additional objects, advantages and novel features of the present invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
A bending die according to a first aspect of the present invention includes a base member (1, 11), which is provided with a first portion (1a, 11a), the root of a lead (5, 16) is in contact with, and a second portion (1b, 11b), the end (5A, 16A) of the lead (5, 16) is in contact with; and a roller (3, 14), provided around the second portion (1b, 11b) of the base member (1, 11) to make rolling contact with the lead (5, 16) in bending operation.
A bending machine according to a second aspect of the present invention includes a bending die (1, 11) which is provided with a first portion (1a, 11a), the root of a lead (5, 16) is in contact with, and a second portion (1b, 11b), the end of the lead (5, 16) is in contact with; a punch (6, 17) which is movable in a specific direction to bend the lead (5, 16); and a roller (3, 14) provided around the second portion (1b, 11b) of the bending die (1, 11) to make rolling contact with the lead (5, 16) in bending operation.